Method and apparatus for wet desulfurization spray towers

ABSTRACT

A method and apparatus or system is provided for cleaning a flue gas and/or cooling a flue gas with a dispersed finely divided absorption liquid. As such, the absorption liquid is dispersed in a wet scrubber through which flue gas flows for absorption liquid and flue gas intermingling and contact to produce a cleaned flue gas. The absorption liquid supplied to the wet scrubber is dispersed from upwardly spraying anti-clogging nozzles and downwardly spraying nozzles arranged to maximize absorption liquid and flue gas contact with minimal spray interference between nozzles.

TECHNICAL FIELD

The present disclosure provides in general a method and apparatus orsystem for cleaning polluted gas and/or cooling of hot gas by contactingthe gas with a finely divided liquid for absorption of gaseouspollutants and/or cooling of the gas. More specifically, the presentdisclosure provides a method and apparatus or system directed to nozzlesresistant to clogging used in a nozzle configuration for cleaningpolluted gas and/or cooling of hot gas by contacting the gas with afinely divided liquid for absorption of gaseous pollutants and/orcooling of the gas.

TECHNICAL BACKGROUND

Cleaning of polluted gas with a view to removing particulate or gaseoussubstances is an important and common process in today's industrializedsociety. A vast variety of techniques have been developed, and todaythere are often several methods to choose between when a gas cleaningplant is to be designed, even when very specific pollutants are to beremoved.

Particulate pollutants are often removed by means of dynamic separators,such as cyclones, electrostatic precipitators or barrier filters, bagfilters or cassette filters.

Gaseous pollutants are generally removed using an additive, either byabsorption by the additive supplied in either dry or wet form, or byreacting gaseous pollutants with the additive supplied in either gaseousor liquid form, so as to obtain a particulate product. The reactionproduct is thereafter separated in a particle separator.

Cooling gas with a view to adapting the gas's temperature or torecovering heat therefrom, is also an important and common process. Heattransfer generally takes place either by means of heat exchangers ofrecuperative or regenerative type or by direct contact between the hotand the cold medium. Since this invention concerns heat transfer bydirect contact between a gas and a liquid, other techniques will not bediscussed.

One method advantageous in many respects consists of conducting a gasthrough a “rain” of finely divided liquid or past surfaces overflowed bya liquid. These methods make it possible to cool a hot gas as well as tocapture particles in the liquid and to absorb or to react gaseouspollutant components of a polluted gas with the liquid. The liquid mayalso contain substances causing or promoting dissolved gaseous pollutantcomponents to form solid particulates for easier separation thereof fromthe liquid.

The liquid is normally recycled in the contact device, but a portionthereof is removed, generally continuously, in order to use its heat inother applications and/or to be treated to separate pollutantstherefrom. Thus the cooled and/or treated liquid can be recycled to thecontact device to be used again.

Polluted gas washing plants can include contact devices or open towerswhere the polluted gas only encounters a finely divided liquid, andpacked scrubbers or packed columns where the polluted gas flows througha tower filled with e.g. saddle-shaped or coil-shaped small parts, ontowhich liquid is sprayed so as to produce a liquid film which flowsdownwardly over essentially the entire total surface. However, sincepacked scrubbers do not fall within the field of the subject disclosure,such will not be discussed further herein.

Examples of contact devices or open towers, e.g. for separating sulphurdioxide from a polluted gas and/or for cooling of the gas in order torecover heat, are disclosed in U.S. Pat. No. 3,532,595. As such, U.S.Pat. No. 3,532,595 discloses both vertical towers and scrubbers withhorizontal gas flow and liquid supplied at several levels or positions.U.S. Pat. No. 4,164,399, discloses a tower of less complex design, whereliquid is supplied only at one level but is distributed after capture atseveral levels. U.S. Pat. No. 2,523,441, discloses a combination of anopen tower with a packed section.

The above-noted techniques require that the liquid used in the contactdevice falls or flows downwardly by gravity. It is however also known todesign contact devices or scrubbers which generate more or lesshorizontal liquid curtains through which the polluted gas flows. Twoexamples are disclosed in U.S. Pat. No. 2,589,956 and U.S. Pat. No.3,691,731.

An intermediate design is disclosed in U.S. Pat. No. 4,583,999, whereinthe washing liquid is supplied horizontally but, after somedeceleration, descends as a rain of finely divided droplets.

Another gas contact device or tower is disclosed in DE-A1 33 41 318 orU.S. Pat. No. 3,532,595, wherein liquid is supplied at 4 to 6 levels.Each level has several nozzles to distribute small liquid droplets forgas and liquid contact. As such, each level is provided with nozzlesarranged with a spacing of 0.5-1 meters (m), in a regular lattice. Thedistance between the levels is 1-2 m. The efficiency of the contactdevice or tower is largely dependent on the relative movement betweenthe droplets and the gas. It is therefore generally preferred that thegas flows upwardly in a direction contrary to the descending liquiddroplets, i.e. counter currently, but for various reasons there alsoexist gas contact devices or towers in which the gas descends in thesame direction as the descending droplets, i.e. concurrently.

If it is desirable to increase the gas treatment efficiency using thismethod, it is necessary either to increase the height of the tower or toincrease the flow of liquid. Whichever option is chosen, the consequenceis increased pump work for a given volume of gas flow. Open gas contactdevices or towers also suffer from the major disadvantage of requiringsignificant space. Significant space requirements also mean significantassociated building costs since the towers typically must be relativelytall. As such, liquid to descend through the tower in the form of a rainof fine droplets must first be pumped up to a considerable height. Suchpump work significantly increases operational costs associated with gastreatment.

Another open spray tower system is disclosed in U.S. Pat. No. 5,474,597.The open spray tower as disclosed uses nozzles arranged in a patternwhereby nozzles spraying liquid upwardly in the same direction as thatof gas flow alternate with nozzles spraying liquid downwardly in theopposite direction as that of gas flow, for purposes of improving masstransfer. A disadvantage of the system is that the nozzles arranged tospray liquid upwardly plug when the system is not in operation andwithout a flow of liquid. When not in operation, accumulated slurry andparticulates from nozzles arranged above spraying liquid downwardlycaused plugging of unused nozzles, or worse yet, back flow intoassociated pumps.

Gas cleaning and gas cooling in wet-type contact devices or scrubbers,has for many decades been a well-established technique in processindustries, power plants and incineration plants. Even with certaindrawbacks, such as those noted above, this technique is well tried andmust be considered both efficient and reliable. However, a significantdrawback to such wet-type contact devices or scrubbers is spray nozzleclogging resulting in inefficient gas cleaning and gas cooling. Thedrawback of spray nozzle clogging needs to be addressed. As such, amethod and/or apparatus that addresses costly nozzle clogging and theinefficient gas cleaning/cooling resulting therefrom is needed.

SUMMARY

The subject disclosure provides both a method and an apparatus or systemthat address costly nozzle clogging and the inefficient gas cleaningand/or gas cooling resulting therefrom. As such, the present disclosurerelates to a method and an apparatus or system for cleaning polluted gasand/or cooling of hot gas, wherein the gas is contacted with a finelydivided liquid for the separation of particulates, absorption of gaseouspollutants and/or cooling of the gas. The finely divided liquid issupplied using anti-clogging nozzles arranged within a pattern ofnozzles in two or more planes substantially perpendicular to the mainflow direction of the gas flowing through the apparatus or system.

To address costly nozzle clogging and resultant inefficient gascleaning/cooling, anti-clogging nozzles are used within a pattern ofnozzles to supply finely divided liquid for contact with a gas for gascleaning and/or gas cooling. The subject anti-clogging nozzles are dualorifice nozzles with a majority of an amount of liquid flow flowing inone first direction, and a relatively small amount of liquid flowflowing in another second direction. The relatively small amount ofliquid flow discharged in the second direction has little effect duringnozzle operation. However, when the nozzle is not in operation, therelatively small amount of liquid flow discharged from the nozzle in thesecond direction provides a drainage route for particulate matter thatwould otherwise clog the opposed nozzle that discharges in the firstdirection. Thereby, the relatively small amount of fluid flow in thesecond direction serves to reduce or eliminate nozzle clogging oftenassociated with the cleaning of polluted gas and/or cooling of hot gas.Also, the subject anti-clogging nozzles reduce or eliminate operationcosts associated with frequent nozzle cleaning and/or replacement aspreviously required.

In summary, the subject apparatus or system comprises a wet scrubberwith at least a first spray level and a second spray level, eachequipped with downwardly spraying nozzles arranged in vertical alignmentone above the other, and upwardly spraying anti-clogging nozzlesalternating between the downwardly spraying nozzles also arranged invertical alignment one above the other. Each of the upwardly sprayinganti-clogging nozzles has an upward extending portion and an opposedextended portion operable for particulate flow from the upward extendingportion to the opposed extended portion to prevent particulate cloggingof the upward extending portion of the upwardly spraying anti-cloggingnozzle. The subject apparatus or system may further comprise additionalspray levels equipped with like arranged downwardly spraying nozzles andupwardly spraying anti-clogging nozzles, such as from 1 to 18 additionalspray levels. As such, a flue gas produced in a boiler flows upwardlythrough the wet scrubber where an absorption liquid is atomized ordispersed as a finely divided spray from at least a portion of thedownwardly spraying nozzles and at least a portion of the upwardlyspraying anti-clogging nozzles. Preferably, about 90% or more of theabsorption liquid dispersed from the upwardly spraying anti-cloggingnozzles is sprayed upwardly from the upward extending portion thereofand about 10% or less of the absorption liquid sprayed from the upwardlyspraying anti-clogging nozzles is sprayed downwardly from the opposedextended portion. Alternatively, preferably, about 80% or more of theabsorption liquid dispersed from the upwardly spraying anti-cloggingnozzles is sprayed upwardly from the upward extending portion thereofand about 20% or less of the absorption liquid sprayed from the upwardlyspraying anti-clogging nozzles is sprayed downwardly from the opposedextended portion. Absorption liquid so sprayed from the nozzles contactsthe flue gas flowing through the wet scrubber and absorbs acid gasestherein to produce a cleaned flue gas. Preferably for this purpose, theabsorption liquid is a limestone absorption liquid or slurry. Tosignificantly reduce or eliminate particulate clogging of the upwardlyspraying anti-clogging nozzles, the same are operable to removeparticulates from the upward extending portion thereof through theopposed, smaller sized, extended portion.

In summary, the subject method comprises supplying an absorption liquidto a wet scrubber with at least a first spray level and a second spraylevel, each spray level equipped with downwardly spraying nozzlesarranged in vertical alignment one above the other, and upwardlyspraying anti-clogging nozzles alternating between the downwardlyspraying nozzles also arranged in vertical alignment one above theother. Each upwardly spraying anti-clogging nozzle includes an upwardextending portion and an opposed extended portion operable forparticulate flow from the upward extending portion to the opposedextended portion to prevent particulate clogging of the upward extendingportion. The subject method further comprises contacting a flue gasproduced in a boiler flowing upwardly through the wet scrubber with theabsorption liquid to produce a cleaned flue gas. According to thesubject method, the wet scrubber may also include additional spraylevels equipped with like arranged downwardly spraying nozzles andupwardly spraying anti-clogging nozzles. The preferred absorption liquidis a limestone absorption liquid or slurry is atomized or dispersed as afinely divided spray from at least a portion of the downwardly sprayingnozzles and at least a portion of the upwardly spraying anti-cloggingnozzles. About 90% or more of the absorption liquid sprayed from theupwardly spraying anti-clogging nozzles is sprayed upwardly from anupward extending portion thereof and about 10% or less of the absorptionliquid sprayed from the upwardly spraying anti-clogging nozzles issprayed downwardly from an opposed extended portion. Alternatively,about 80% or more of the absorption liquid sprayed from the upwardlyspraying anti-clogging nozzles is sprayed upwardly from an upwardextending portion thereof and about 20% or less of the absorption liquidsprayed from the upwardly spraying anti-clogging nozzles is sprayeddownwardly from an opposed extended portion. Accordingly, the upwardlyspraying anti-clogging nozzles are operable for particulate removal fromthe upward extending portion thereof through the opposed, smaller sized,extended portion.

Further objects and features of the present disclosure will be apparentfrom the following description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to theaccompanying drawings, in which:

FIG. 1 is schematic cross-sectional view of a wet scrubber systemaccording to the subject embodiment;

FIG. 2 is an enlarged schematic side view of the circled nozzles of FIG.1 referenced as II;

FIG. 3 is a schematic top view of the nozzles of FIG. 2; and

FIG. 4 is a schematic side cross sectional view of the nozzles of FIG.2.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates the subject apparatus or system 10comprising a wet scrubber 12 useful for cleaning a polluted process gasand/or for cooling a hot process gas. Spray apparatus 13 in wet scrubber12 is operative for removing at least a portion of a sulphur dioxidecontent of a process gas, in the form of a flue gas, FG, generated in aboiler 15 operative for combusting a fuel F, such as coal or oil. Fluegas FG flows from boiler 15 through fluidly connected duct 15 a intofluidly connected inlet 16 of wet scrubber 12.

The wet scrubber 12 comprises a vertical open tower 14, an inlet 16 forflue gas FG to be cleaned and/or cooled, and an outlet 18 for cleanedflue gas CG from which at least a portion of the sulphur dioxide contenthas been removed. An absorption liquid tank 20 is arranged at a bottom22 of the vertical open tower 14. The absorption liquid tank 20 isprovided with an oxidation arrangement 22. Fresh limestone, CaCO₃, issupplied to the absorption liquid tank 20 through an inlet 28 a from anabsorbent supply device 24 comprising a limestone storage 26 fluidlyconnected to a supply pipe 28 fluidly connected to inlet 28 a. It willbe appreciated that absorption liquid tank 20 may, as an alternative, bepositioned outside of vertical open tower 14, and that the supply offresh limestone could, as an alternative, enter the vertical open tower14 at locations other than the absorption liquid tank 20, as a drypowder, a slurry or both.

The wet scrubber 12 further comprises a first circulation pump 30 whichcirculates through a fluidly connected absorption liquid circulationpipe 32, a limestone absorption liquid, sometimes referred to as alimestone slurry, from the absorption liquid tank 20 to a fluidlyconnected first spray level system 34 positioned vertically lowest andwithin closest proximity to bottom 22 within vertical open tower 14. Thewet scrubber 12 further comprises a second circulation pump 36 whichcirculates through a fluidly connected absorption liquid circulationpipe 38, a limestone absorption liquid from the absorption liquid tank20 to a fluidly connected second spray level system 40 positionedvertically above first spray level system 34 within vertical open tower14, and a third circulation pump 42 which circulates through a fluidlyconnected absorption liquid circulation pipe 44, a limestone absorptionliquid from the absorption liquid tank 20 to a fluidly connected thirdspray level system 46 positioned vertically above second spray levelsystem 40 and the greatest distance from bottom 22 within vertical opentower 14. A vertical distance, illustrated as a distance CC in FIG. 1,between the mid-point of the first spray level system 34 and themid-point of the second spray level system 40, as well as a verticaldistance, also shown as a distance CC in FIG. 1, between the mid-pointof the second spray level system 40 and the mid-point of the third spraylevel system 46, is approximately 1.25 meters (m) to approximately 3 m.A distance CC less than approximately 1.25 m is less preferable, sincesuch distance tends to cause unwanted interactions between adjacentspray level systems, resulting in a decreased sulphur dioxide removalefficiency. A distance CC which greater than approximately 3 m is lesspreferable, since such distance tends to result in a very high overallheight of the vertical open tower 14, increasing investment andoperating costs associated therewith.

The first spray level system 34 comprises a first tubular portion 48 anda plurality of fluidly connected atomizing nozzles 50 and 52 thatatomize or disperse as a finely divided spray a limestone absorptionliquid circulated thereto by the pump 30. As such, the finelydistributed limestone absorption liquid achieves effective contact withflue gas FG passing substantially vertically upwardly through the wetscrubber 12. The second spray level system 40 likewise comprises asecond tubular portion 54 and a plurality of fluidly connected atomizingnozzles 50 and 52. The third spray level system 46 likewise comprises athird tubular portion 56 and a plurality of fluidly connected atomizingnozzles 50 and 52. The atomizing nozzles 50 and 52 of the second tubularportion 54 and third tubular portion 56 are of the same or of a similartype as the atomizing nozzles 50 and 52 of the first tubular portion 48.

All or a vast majority of atomizing nozzles 50 spray in a singulardirection, i.e., in a cone pattern directed essentially downwardlywithin vertical open tower 14 counter current to the flow of flue gas FGtherethrough. Atomizing nozzles 50 may, for example, be of the type4CF-303120, available from Spraying Systems Co, Wheaton, Ill., USA. Thistype of atomizing nozzle 50 is operative for a liquid flow of about 70m³/hour, corresponding to 70000 litres/hour, or 1170 litres/minute, at aspraying pressure measured using water, of about 0.5 bar, as well as aliquid flow of about 107 m³/hour, corresponding to 107000 litres/hour,or 1780 litres/minute, at a spraying pressure measured using water, ofabout 1.2 bar.

All of atomizing nozzles 52 are anti-clogging nozzles that spray in atleast two directions, i.e., in a cone pattern directed essentiallyupwardly within vertical open tower 14 in essentially the same directionof flow as that of flue gas FG therethrough, and to a lesser extent, ina downwardly and/ or a near downward direction counter current to theflow of flue gas FG through vertical open tower 14. Atomizing nozzles 52of the type described herein are commercially available from SprayingSystems Co, Wheaton, Ill., USA. During operation of first spray level34, second spray level 40 and/or third spray level 46, about 90% toabout 99% or more of the absorption liquid sprayed from anti-cloggingnozzles 52 is sprayed in a cone pattern upwardly from upward extendingportion 58. As such, anti-clogging nozzle 52 is operative for an upwardliquid flow of about 63 m³/hour to about 69 m³/hour, corresponding toabout 63000 litres/hour to about 69000 litres/hour, or about 1050litres/minute to about 1150 litres/minute, at a spraying pressuremeasured using water, of about 0.5 bar, as well as a liquid flow ofabout 96 m³/hour to about 106 m³/hour, corresponding to about 96000litres/hour to about 106000 litres/hour, or about 1600 litres/minute toabout 1766 litres/minute, at a spraying pressure measured using water,of about 1.2 bar. Alternatively, during operation of first spray level34, second spray level 40 and/or third spray level 46, about 80% or moreof the absorption liquid sprayed from anti-clogging nozzles 52 issprayed in a cone pattern upwardly from upward extending portion 58.

During operation of first spray level 34, second spray level 40 and/orthird spray level 46, about 10% to about 1% or less of the absorptionliquid sprayed from anti-clogging nozzles 52 is sprayed downwardlyand/or in a near downward direction from extended portions 60. As such,anti-clogging nozzle 52 is operative for an downward liquid flow ofabout 6.3 m³/hour to about 6.9 m³/hour, corresponding to about 6300litres/hour to about 6900 litres/hour, or about 105 litres/minute toabout 115 litres/minute, at a spraying pressure measured using water, ofabout 0.5 bar, as well as a liquid flow of about 9.6 m³/hour to about10.6 m³/hour, corresponding to about 9600 litres/hour to about 10600litres/hour, or about 160 litres/minute to about 176 litres/minute, at aspraying pressure measured using water, of about 1.2 bar. Alternatively,during operation of first spray level 34, second spray level 40 and/orthird spray level 46, about 20% or less of the absorption liquid sprayedfrom anti-clogging nozzles 52 is sprayed downwardly and/or in a neardownward direction from extended portions 60.

When first spray level 34, second spray level 40 and/or third spraylevel 46 are not in operation, little to no absorption liquid is sprayedfrom upward extending portions 58 while about 10% to about 1% or less,or alternatively about 20% or less, of the absorption liquid is sprayeddownwardly and/or in a near downward direction from opposed extendedportions 60. This continued fluid flow through extended portions 60during periods of non-operation provides a direct drainage route forparticulates collected in upward extending portions 58 therebysignificantly reducing or eliminating particulate clogging thereof. Assuch, when not in operation, anti-clogging nozzles 52 maintain a liquidflow as needed from extended portion 60 of about 6.3 m³/hour to about6.9 m³/hour, corresponding to about 6300 litres/hour to about 6900litres/hour, or about 105 litres/minute to about 115 litres/minute, at aspraying pressure measured using water, of about 0.5 bar, as well as aliquid flow of about 9.6 m³/hour to about 10.6 m³/hour, corresponding toabout 9600 litres/hour to about 10600 litres/hour, or about 160litres/minute to about 176 litres/minute, at a spraying pressuremeasured using water, of about 1.2 bar. However, when not in operation,spraying pressure will typically be reduced thus reducing liquid flow toa level appropriate and a time period appropriate to prevent clogging ofupward extending portion 58, depending on limestone and like particulatelevels within wet scrubber 12.

Atomizing nozzles 50 and 52 are arranged in a specific pattern on firsttubular portion 48, second tubular portion 54 and third tubular portion56. As such, on each first, second and third tubular portions 48, 54 and56 respectively, nozzles 50 are arranged to alternate with nozzles 52along the lengths thereof. Also, on each first, second and third tubularportions 48, 54 and 56 respectively, nozzles 50 are each verticallyarranged one above or nearly above another, and nozzles 52 are eachvertically arranged one above or nearly above another. Nozzles 50 and 52are so arranged to minimize spray interference between nozzles andmaximize spray and flue gas FG contact for efficient flue gas FGcleaning. Optionally, rather than having two different types of nozzles50 and 52 available for installation/maintenance purposes, only nozzles52 could be utilized with half of nozzles 52 positioned with a majorityof absorption liquid flow dispersed upwardly and the other half ofnozzles 52 positioned with a majority of absorption liquid flowdispersed downwardly, thereby replacing nozzles 50. However, sincenozzles 52 are typically more expensive than nozzles 50, such is not thepreferred arrangement and therefore for purposes of clarity is notdiscussed further herein.

A mist eliminator 62 is located above the third spray level system 46.The mist eliminator 62 removes at least a portion of the absorptionliquid droplets entrained by the cleaned flue gas, CG.

In wet scrubber 12, sulphur dioxide, SO₂, in the flue gas FG reacts withthe limestone, CaCO₃, of the absorption liquid to form calcium sulphite,CaSO₃, which is subsequently oxidized to form gypsum, CaSO₄. Theoxidation of calcium sulphite is preferably performed by bubbling air oroxygen gas through the absorption liquid using oxidation arrangement 24.Hence, the absorption liquid comprises, in addition to the limestone,also small amounts of calcium sulphite and, as a major constituent,gypsum. The gypsum formed through this process is removed from theabsorption liquid tank 20 via a disposal pipe 64 and is forwarded to agypsum dewatering unit, schematically indicated as belt filter 66. Thedewatered gypsum may be commercially used, for example in wallboardproduction.

In addition to sulphur dioxide, SO₂, the wet scrubber 12 will remove, atleast partly, also other contaminants from the flue gas FG. Examples ofsuch other contaminants include sulphur trioxide, SO₃, hydrochloricacid, HCl, hydrofluoric acid, HF, and other acid contaminants. Stillfurther, the wet scrubber 12 may also remove, at least partly, othertypes of contaminants from the flue gas, such as for example dustparticles and mercury.

A control unit 68 controls operation of wet scrubber 12. To this end, acontrol device in the form of a first control valve 70 is provided onthe first tubular portion 48 of the first spray level system 34, and acontrol device in the form of a second control valve 72 is provided onthe second tubular portion 54 of the second spray level system 40.Furthermore, a control device in the form of a third control valve 74 isprovided on the third tubular portion 56 of the third spray level system46. The control unit 68 controls, individually, each of the valves 70,72 and 74, for efficient operation of wet scrubber 12.

FIG. 2 schematically illustrates nozzles 50 and 52 of FIG. 1, circledand identified by reference II. As such, nozzle 50 sprays in a downwarddirection as described above, and nozzle 52 is a dual orificeanti-clogging nozzle that sprays absorption liquid predominantly in anupward direction from upward extending portion 58 and to a lesser extentin a downward direction from opposed extended portion 60.

FIG. 3 schematically illustrates from a top view looking down intovertical open tower 14 nozzles 50 and 52 of FIG. 2. As such, withinupward extending portion 58 is spray orifice 76 through which absorptionliquid is dispersed from first tubular portion 48.

FIG. 4 again illustrates nozzles 50 and 52 of FIG. 2. Spray orifice 76of upward extending portion 58 of nozzle 52 is sized approximately thesame as that of spray orifice 80 of nozzle 50. However, spray orifice 78within extended portion 60 of nozzle 52 is sized considerably smallerthan spray orifices 76 and 80, since fluid flow therethrough isconsiderably less. Also, spray orifice 78 is aligned below and with thatof spray orifice 76 to allow a flow of particulates from upwardextending portion 58 downwardly through spray orifices 76 and 78 forrelease from extended portion 60 thereby significantly reducing oreliminating particulate clogging of upward extending portion 58.

In using the wet scrubber 12 to clean or treat a flue gas FG produced ina boiler 15, the flue gas FG is passed upwardly through wet scrubber 12for contact with an absorption liquid, such as a limestone slurry or thelike, atomized or dispersed as a finely divided spray from nozzles 50and 52 arranged in a pattern on at least a first spray level 34 and asecond spray level 40. The atomized or finely divided absorption liquidspray absorbs pollutants such as sulphur dioxide, hydrogen chloride andlike acids from the flue gas upon contact therewith to produce a cleanedflue gas CG. To maximize absorption liquid and flue gas FG contact,nozzles 50 are arranged to alternate with nozzles 52 along lengths of atleast first spray level 34 and second spray level 40, with nozzles 50arranged vertically one above another and nozzles 52 arranged verticallyabove one another along the lengths of at least first spray level 34 andsecond spray level 40. Nozzles 50 are arranged vertically one aboveanother and nozzles 52 are arranged vertically above one another on theat least first spray level 34 and second spray level 40 to maximizeabsorption liquid and flue gas FG contact while minimizing absorptionliquid spray interference between nozzles. Additionally, nozzles 52 areanti-clogging nozzles with 90% or more fluid flow therethrough flowingfrom upward extending portion 58 and 10% or less fluid flow therethroughflowing from opposed extended portion 60, thereby providing a route ofparticulate flow from upward extending portion 58 to and out fromopposed extended portion 60 to significantly reduce or eliminateparticulate clogging of upward extending portion 58 when not in use.Alternatively, nozzles 52 are anti-clogging nozzles with 80% or morefluid flow therethrough flowing from upward extending portion 58 and 20%or less fluid flow therethrough flowing from opposed extended portion60, thereby providing a route of particulate flow from upward extendingportion 58 to and out from opposed extended portion 60 to significantlyreduce or eliminate particulate clogging of upward extending portion 58when not in use.

While the invention has been described with reference to a number ofpreferred embodiments, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the presentdisclosure. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the subjectdisclosure without departing from the essential scope thereof.Therefore, it is intended that the disclosure not be limited to theparticular embodiments disclosed as the best mode contemplated forcarrying out the same, but that the subject disclosure will include allembodiments falling within the scope of the appended claims. Moreover,the use of the terms first, second, etc. do not denote any order orimportance, but rather the terms first, second, etc. are used todistinguish one element from another.

In summary, the subject apparatus or system 10 comprises a wet scrubber12 with at least a first spray level 34 and a second spray level 40,each equipped with downwardly spraying nozzles 50 on each the firstspray level 34 and the second spray level 40 arranged in verticalalignment one above the other, and upwardly spraying anti-cloggingnozzles 52 alternating between the downwardly spraying nozzles 50 oneach the first spray level 34 and the second spray level 40 alsoarranged in vertical alignment one above the other. Each of the upwardlyspraying anti-clogging nozzles 52 has an opposed extended portion 60operable for particulate flow from an upward extending portion 58 of theupwardly spraying anti-clogging nozzle 52 therethrough to preventparticulate clogging of the upward extending portion 58 when not inoperation. The subject apparatus or system 10 may further compriseadditional spray levels 13 equipped with like arranged downwardlyspraying nozzles 50 and upwardly spraying anti-clogging nozzles 52, suchas from 1 to 18 additional spray levels 13. As such, a flue gas FG froma boiler 15 flows upwardly through the wet scrubber 12 where anabsorption liquid is atomized or sprayed from at least a portion of thedownwardly spraying nozzles 50 and at least a portion of the upwardlyspraying anti-clogging nozzles 52. Preferably, about 90% or more of theabsorption liquid sprayed from the upwardly spraying anti-cloggingnozzles 52 is sprayed upwardly from an upward extending portion 58thereof and about 10% or less of the absorption liquid sprayed from theupwardly spraying anti-clogging nozzles 52 is sprayed downwardly from anopposed extended portion 60. Alternatively, about 80% or more of theabsorption liquid sprayed from the upwardly spraying anti-cloggingnozzles 52 is sprayed upwardly from an upward extending portion 58thereof and about 20% or less of the absorption liquid sprayed from theupwardly spraying anti-clogging nozzles 52 is sprayed downwardly from anopposed extended portion 60. Absorption liquid so sprayed from each ofthe nozzles 50 and 52 contacts the flue gas FG flowing through the wetscrubber 12 absorbing acid gases therein to produce a cleaned flue gasCG. Preferably for this purpose, the absorption liquid is a limestoneabsorption liquid or slurry. As such, to significantly reduce oreliminate particulate clogging, the upwardly spraying anti-cloggingnozzles 52 are operable for particulate removal from an upward extendingportion 58 thereof through an aligned smaller sized extended portion 60.

In summary, the subject method comprises supplying an absorption liquidto a wet scrubber 12 with at least a first spray level 34 and a secondspray level 40, each equipped with downwardly spraying nozzles 50arranged in vertical alignment one above the other, and upwardlyspraying anti-clogging nozzles 52 alternating between the downwardlyspraying nozzles 50 also arranged in vertical alignment one above theother. Each of the upwardly spraying anti-clogging nozzles 52 includesan opposed downwardly draining extended portion 60 operable forparticulate flow from an upward extending portion 58 of the upwardlyspraying anti-clogging nozzle 52 to and out from extended portion 60 toprevent particulate clogging of the upward extending portion 58 of theupwardly spraying anti-clogging nozzle 52. The subject method furthercomprises contacting a flue gas FG produced in a boiler 15 flowingupwardly through the wet scrubber 12 with an absorption liquid spray toproduce a cleaned flue gas CG. According to the subject method, the wetscrubber 12 may also include additional spray levels 13 equipped withlike arranged downwardly spraying nozzles 50 and upwardly sprayinganti-clogging nozzles 52. As such, the absorption liquid, preferably alimestone absorption liquid or slurry, is atomized or dispersed as afinely divided spray from at least a portion of the downwardly sprayingnozzles 50 and at least a portion of the upwardly spraying anti-cloggingnozzles 52. Preferably about 90% or more of the absorption liquidsprayed from the upwardly spraying anti-clogging nozzles 52 is sprayedupwardly from an upward extending portion 58 and about 10% or less ofthe absorption liquid sprayed from the upwardly spraying anti-cloggingnozzles 52 is sprayed downwardly from an opposed extended portion 60.Alternatively, about 80% or more of the absorption liquid sprayed fromthe upwardly spraying anti-clogging nozzles 52 is sprayed upwardly froman upward extending portion 58 and about 20% or less of the absorptionliquid sprayed from the upwardly spraying anti-clogging nozzles 52 issprayed downwardly from an opposed extended portion 60. Accordingly, theupwardly spraying anti-clogging nozzles 52 are operable for particulateremoval from the upward extending portion 58 through the opposed,smaller sized, extended portion 60.

It will be appreciated that numerous variants of the embodimentsdescribed above are possible within the scope of the appended claims.

1. A system comprising: a wet scrubber with at least a first spray leveland a second spray level; downwardly spraying nozzles on each the firstspray level and the second spray level arranged in vertical alignmentone above the other; upwardly spraying anti-clogging nozzles alternatingbetween the downwardly spraying nozzles on each the first spray leveland the second spray level also arranged in vertical alignment one abovethe other; and each upwardly spraying anti-clogging nozzle comprising anupward extending portion and an opposed extended portion operable forparticulate flow from the upward extending portion to the opposedextended portion to prevent particulate clogging of the upward extendingportion.
 2. The system of claim 1 further comprising additional spraylevels equipped with like arranged downwardly spraying nozzles andupwardly spraying anti-clogging nozzles.
 3. The system of claim 1wherein a flue gas from a boiler flows upwardly through the wetscrubber.
 4. The system of claim 1 wherein an absorption liquid isatomized or dispersed from at least a portion of the downwardly sprayingnozzles and at least a portion of the upwardly spraying anti-cloggingnozzles.
 5. The system of claim 1 wherein an absorption liquid isatomized or dispersed from at least a portion of the downwardly sprayingnozzles and at least a portion of the upwardly spraying anti-cloggingnozzles with about 80% or more, or about 90% or more of the absorptionliquid sprayed from the upwardly spraying anti-clogging nozzles sprayedupwardly from an upward extending portion and about 20% or less, orabout 10% or less of the absorption liquid sprayed from the upwardlyspraying anti-clogging nozzles sprayed downwardly from an opposedextended portion.
 6. The system of claim 1 wherein an absorption liquidis atomized or dispersed from each of the nozzles for contact with aflue gas flowing through the wet scrubber to produce a cleaned flue gas.7. The system of claim 1 wherein each of the nozzles are operable toatomize or disperse a limestone absorption liquid or slurry.
 8. Thesystem of claim 1 wherein each of the upwardly spraying anti-cloggingnozzles are operable for particulate removal from an upward extendingportion out through an opposed, smaller sized, extended portion.
 9. Amethod comprising: supplying an absorption liquid to a wet scrubber withat least a first spray level and a second spray level equipped withdownwardly spraying nozzles on each the first spray level and the secondspray level arranged in vertical alignment one above the other, andupwardly spraying anti-clogging nozzles alternating between thedownwardly spraying nozzles on each the first spray level and the secondspray level also arranged in vertical alignment one above the other,with each upwardly spraying anti-clogging nozzle including a downwardlydraining extended portion operable for particulate flow from an upwardextending portion of the upwardly spraying anti-clogging nozzle toprevent particulate clogging of the upward extending portion; andcontacting a flue gas flowing through the wet scrubber with theabsorption liquid to produce a cleaned flue gas.
 10. The method of claim9 further comprising adding additional spray levels equipped with likearranged downwardly spraying nozzles and upwardly spraying anti-cloggingnozzles.
 11. The method of claim 9 wherein flue gas produced in a boilerflows upwardly through the wet scrubber.
 12. The method of claim 9wherein the absorption liquid is atomized or dispersed as a finelydivided spray from at least a portion of the downwardly spraying nozzlesand at least a portion of the upwardly spraying anti-clogging nozzles.13. The method of claim 9 wherein the absorption liquid is a limestoneabsorption liquid or slurry atomized or dispersed from at least aportion of the downwardly spraying nozzles and at least a portion of theupwardly spraying anti-clogging nozzles with about 80% or more, or 90%or more of the absorption liquid sprayed from the upwardly sprayinganti-clogging nozzles is sprayed upwardly from an upward extendingportion and about 20% or less, or about 10% or less of the absorptionliquid sprayed from the upwardly spraying anti-clogging nozzles issprayed downwardly from an opposed extended portion.
 14. The method ofclaim 9 wherein the absorption liquid is a limestone slurry sprayed fromeach of the nozzles for contact with flue gas flowing upwardly throughthe wet scrubber to produce a cleaned flue gas.
 15. The method of claim9 wherein each of the upwardly spraying anti-clogging nozzles areoperable for particulate removal from an upward extending portionthrough an opposed, smaller sized, extended portion.